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Aviation History
1951
1951 - 2102.PDF
19 '•OCTOBER I95 1 FLIGHT H & C or The Vapours or, simply, Tank Losses ON one flank of my favourite tobacco tin, in verysmall letters, runs the legend " Sold subject to loss in weight by evaporation." Similar inscriptions on the labels of bottles remind me to replace the cork or cap. Well, I'm not grumbling : I pay for my tobacco and liquids with money that is notoriously subject to loss by inflation. Fair's fair. Come to think of it, nearly everything and everybody these days is subject to loss by evaporation, inflation or volatility—call it what you will. Even aircraft fuels. Let me explain. Turbine fuels, as used in modern gas turbine-engined aircraft, are very similar chemically to ordinary domestic paraffin : you know—the stuff that looks something like this to the naked eye of a research chemist: In other words the volatile hydrocarbons are subject to loss by evaporation. No, sir, this is not a diagram showing the arrangement of taps (faucets ?) in a Hollywood bathroom : it's a picture of a droplet of paraffin, its skeleton or molecular structure. Turbine fuels then—whether they're the unidentical twin of domestic paraffin or some mixture of kerosene, heavy petrol and light diesel oil—all contain a fair proportion of relatively volatile hydrocarbons. Now when fuel is carried in a modern jet aircraft it will evolve vapour on attaining height and these vapours tend to escape into the atmosphere via the tank vents of the aircraft. Fortunately this loss can be minimized, is minimized by the researchers who inhabit the " Esso " laboratories. And they keep on minimizing it.* It's all a matter of how they arrange the "H's" and "C's" and etceteras, or so I'm given to understand. There's another thing. All hydrocarbon fuels contain dissolved air, which is released when the liquid is warmed or depressurized (to coin a barbarous term !). Sometimes this release is violent, so violent that even liquid fuel is carried away with the escaping air. More losses. Fuel manufacturers appreciate this—the process is fundamental to the behaviour of all petroleum fuels— and they can help the aircraft manufacturers by providing data on the behaviour of fuels over a range of tempera- tures and pressures. And this is precisely what " Esso '* scientists do do.* They work hand in glove with the men who design and build Britain's aircraft. * Two more reasons, surely, why frpays fo say FOR ALL PETROLEUM PRODUCTS PETROLEUM COMPANY, LIMITED, 36 QUEEN ANNE'S GATE. LONDON, S.W.
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